Originally Posted by
Recycled Flyer
Just having reread all of this I realized that there is an uncanny parallel between this new contra piston design and tapered cup expansion plugs or "Welch Plugs" that are used in full sized engines.
Couple that with the twice mentioned top of the cylinder "the contra piston end will just enter the top of the cylinder bore" and "and pressed into the cylinder top" and its not hard to believe that the contra was 'meant' to be installed that way.
Yes, a conical contra would work well even in a parallel bore, but it would have to be entered from the top...
Once in the bore it would also be easier to move down, as compared to moving it up. Hmm, I think I have few engines that will act just like that when warm...